WebMD/ December 14, 2011, 6:00 PM

Studies identify stillbirth risk factors, causes

Although many risk factors for stillbirth are out of a woman's control, others can be changed to help lower risk, new research shows.

The cause of death can be identified for many stillbirths, researchers have also found. That can help parents heal.

"The good news is, a lot of the risk factors that are known early [in pregnancy] are changeable," says researcher George Saade, MD, professor of obstetrics and gynecology and chief of the division of maternal-fetal medicine at the University of Texas Medical Branch at Galveston.

Among those, he and his colleagues found, are losing weight, if needed, and not using illegal drugs. Another risk factor is not smoking during the three months before pregnancy occurs, they found.

Stillbirth, defined as fetal death at 20 weeks into the pregnancy or later, affects one in 160 U.S. pregnancies. In the U.S., about 26,000 infants are stillborn each year. After a decline in stillbirth from 1990 to 2003, the rate has been stagnant.

The new research, funded by the Eunice Kennedy Shriver National Institute of Child Health and Human Development, was conducted by the Stillbirth Collaborative Research Network. It was set up to address stillbirth as a public health issue.

The research is published as two studies in the Journal of the American Medical Association.

Stillbirth: Risk Factors Known in Early Pregnancy

Saade and his colleagues evaluated 614 stillborn infants, comparing them to 1,816 infants delivered healthy. The study was done between March 2006 and September 2008 at 59 U.S. hospitals.

After evaluating a number of factors, they found many maternal factors associated with stillbirth. They include:

Being African-American
Having diabetes
Being age 40 or older
Having AB blood type
Having a history of illegal drug use with addiction
Smoking cigarettes in the three months before getting pregnant
Being overweight or obese
Not living with a partner
Having a previous stillbirth
Carrying multiples

The odds of stillbirth for each risk factor ranged. Smoking during the three months before pregnancy, for instance, raised the odds about 1.5 times; previous stillbirth nearly six-fold.

The research results point to the need for good prenatal care and counseling, Saade tells WebMD. "It's important to start prenatal care early, so that any of these risk factors can be addressed," he says.

Even so, he says, the changeable risk factors "still account for a rather small proportion of the risk,'' probably less than a quarter of cases, he says. Other risk factors are still unknown, he says.

Eventually, the list of risk factors will be even longer, Saade says.

However, he says, some unchangeable risk factors aren't as strong as people may believe.

Even though a woman who has had one stillbirth is at increased risk of another, he says, "the majority of women with a previous stillbirth have a live birth in a subsequent pregnancy."

One major strength of this new study, Saade tells WebMD, is that it looks at an entire population, not just stillbirths from one hospital or one region. This makes the results more valid.

Stillbirth: Causes of Death

In a second study, researchers conducted autopsies on stillborn infants. The study was done from March 2006 to September 2008 at the 59 hospitals. They found a probable or possible cause of death in 390 of them, with 312 of them having a probable cause.

"A cause of death can be found in the majority of cases," says study researcher Bob Silver, MD, professor of obstetrics and gynecology at the University of Utah in Salt Lake City.

Most commonly, the causes of death were:

Obstetric complications
Placental abnormalities
Fetal genetic or structural abnormalities
Infection
Umbilical cord abnormalities
High blood pressure or other health problems in the mother

African-American mothers were more likely to have a stillbirth than women of other races, with 43% of black women (but 23% of women of other races) experiencing a stillbirth.

Silver tells WebMD that many parents are reluctant to undergo an autopsy on the fetus. However, he encourages them to do so. "We think it's really important to find a cause," he says. "It helps facilitate emotional healing and closure for parents."

"Almost invariably, they want to think about another pregnancy," he says of parents who have a stillborn infant. With the information from the autopsy, an evaluation of the placenta, and genetic testing on the baby, he says, the parents can be counseled about future pregnancies.

Stillbirths: Perspective on Causes, Risk Factors

The two new studies are an important contribution in an under-studied research area, says Gene Burkett, MD, professor of obstetrics and gynecology in the maternal-fetal medicine division at the University of Miami Miller School of Medicine. He reviewed the findings but was not involved in the research.

"If we can find the risk factors and make a pointed effort to deal with the risk factors, we can lower the incidence of stillbirths," he says.

Burkett heads an effort to reduce stillbirth at his university. One of the causes noted by Silver's group, placental problems, may actually reflect underlying health conditions that need treatment, Burkett says.

Even so, the findings point to the need for good and early prenatal care, he says, especially for those known now to be at higher risk.

By Kathleen Doheny

Reviewed by Louise Chang, MD

SOURCES:The Stillbirth Collaborative Research Network Writing Group. Journal of the American Medical Association, Dec. 14, 2011.Iams, J. Journal of the American Medical Association, Dec. 14, 2011.Gene Burkett, MD, professor of obstetrics and gynecology in the maternal-fetal medicine division, University of Miami Miller School of Medicine.Bob Silver, MD, professor of obstetrics and gynecology, University of Utah, Salt Lake City.George Saade, MD, professor of obstetrics and gynecology and chief of the division of maternal-fetal medicine at the University of Texas Medical Branch at Galveston.